Problems with modems/Example config for QMI-based modem,


We want to integrate different modems into our embedded system. Recently, our Linux-distributor decided to introduce NetworkManager. When we switch to NetworkManager, network connectivity via 3G/2G is never reliable: the connection either succeeds only sporadically or not at all. This happens on three types of modems from two different vendors. When we set up the modems manually with pppd or with a QMI test program, everything works fine an reliably, also automatically after boot. Could you give me advice what steps to do to produce debug/log output to then come back here and have someone look at it?

Furthermore, it would be really nice to have an example configuration file for /etc/NetworkManager/system-connections/ to configure a modem with QMI connection. All the examples I had so far (seem to) only establish the connection with pppd.

Another problem is that it often happens that we use NetworkManager on devices which changes some settings and afterwards we can't even use the old methods to establish a connection. This is really scary since it basically renders our devices unusable so far. Is it possible to tell NetworkManager to put the device in the original state again after using it?

I also have a question to ModemManager but don't know whether I'm right with it here: We want to send AT commands to the modems while they serve an internet connection. Normally, this is possible since the Modems all have multiple serial interfaces. But when using ModemManager, it locks all serial interfaces of the modems and we can't use them anymore. I know that ModemManager can send AT commands with "mmcli --command" but only in debug mode, so apparently not for production use. Is it possible to send commands another way with ModemManager or prevent it from locking all AT interfaces?

Thank you and All the Best,

Jakob Hasse
Software Developement

E: jakob hasse smart-home-technology ch
T: +41 44 552 02 66

Smart Home Technology GmbH

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